Field of the Invention
The present invention relates to a high-quality dye-sensitized solar cell with high photoelectric conversion efficiency, which is obtained at low costs.
Description of the Related Art
In recent years, an environmental issue such as global warming, resulting from the increase of carbon dioxide, has become so serious that measures thereagainst have been promoted on a worldwide basis. Above all, active research and development on a solar cell utilizing solar light energy have been promoted as a clean energy source with fewer burdens on the environment. A monocrystal silicon solar cell, a polycrystalline silicon solar cell, an amorphous silicon solar cell and a compound semiconductor solar cell, and the like have been already put to practical use as such a solar cell, but yet the problem is that these solar cells require high production costs. Thus, a dye-sensitized solar cell has been receiving attentions, researched and developed as a solar cell with fewer environmental burdens, which may decrease production costs.
FIGS. 4A and 4B are each a schematic cross-sectional view showing an example of a general dye-sensitized solar cell. As shown in FIG. 4A, a general dye-sensitized solar cell 100 comprises: an oxide semiconductor electrode substrate 110 having: a first electrode base material 111 having a transparent base material 111b and a transparent electrode layer 111a formed on the transparent base material 111b, and a porous layer 112 formed on the transparent electrode layer 111a and containing a dye-sensitizer-supported fine particle of a metal oxide semiconductor; a counter substrate 120 having: a second electrode base material 121 provided with a function as an electrode, and a catalyst layer 122 formed on the second electrode base material 121; an electrolyte layer 130 formed between the oxide semiconductor electrode substrate 110 and the counter substrate 120 so as to contact with the porous layer 112; and a sealing agent 140 for sealing the dye-sensitized solar cell 100. Then, the dye sensitizer adsorbed in a surface of the fine particle of a metal oxide semiconductor in the porous layer 112 is excited by receiving solar light from the oxide semiconductor electrode substrate 110 side, and an excited electron is conducted to the transparent electrode layer 111a and conducted to the second electrode base material 121 through an external circuit. Thereafter, the returning of the electron to a ground level of the dye sensitizer through a redox pair causes electric power generation.
FIG. 4A is showing as an example a dye-sensitized solar cell of the so-called ‘sequential structure cell type’ such that the first electrode base material 111 has transparency and solar light is received from the oxide semiconductor electrode substrate 110 side. Also, a dye-sensitized solar cell having a constitution of the so-called ‘inverse structure cell type’ such that the second electrode base material 121 has transparency and solar light is received from the counter substrate 120 side is known as exemplified in FIG. 4B. In FIG. 4B, the second electrode base material 121 has a transparent base material 121b and a transparent electrode layer 121a formed on the transparent base material 121b, and the first electrode base material 111 does not have transparency.
Although not shown in the drawing, the above-mentioned dye-sensitized solar cell occasionally has a constitution such that the first electrode base material and the second electrode base material are each base materials having transparency and solar light may be received from either the oxide semiconductor electrode substrate side or the counter substrate side.
Here, in the case of using a liquid electrolyte layer as the above-mentioned electrolyte layer, the sealing needs to be strictly performed by the sealing agent, and the like for preventing liquid spill from the liquid electrolyte layer, however, there has been a problem in durability and stability to maintain the sealing state over a long period since inconveniences such as evaporation of a solvent molecule and solvent disappearance due to liquid spill are occasionally caused.
Since a certain film thickness is necessary for the above-mentioned sealing agent and a certain thickness is also necessary for the electrolyte layer in order to seal the above-mentioned dye-sensitized solar cell, there has been a problem that the dye-sensitized solar cell is formed into a thin film with difficulty.
Thus, it has been studied that a polymer electrolyte layer solidified by making the electrolyte layer contain a polymeric compound is used as the above-mentioned electrolyte layer (Japanese Patent Application Publication No. 2005-019132). In the case of using the above-mentioned polymer electrolyte layer, liquid spill and the like may be restrained from occurring and the polymer electrolyte layer may be formed into a thin film by reason of not requiring the above-mentioned sealing agent.
However, also it is difficult for the above-mentioned polymer electrolyte layer containing only the polymeric compound to sufficiently retain the above-mentioned redox pair, and in a severe use environment of the dye-sensitized solar cell, a problem such that leakage of the redox pair from the above-mentioned polymer electrolyte layer is occasionally caused to deteriorate the dye-sensitized solar cell has been occurred.
The further improvement of photoelectric conversion efficiency has been demanded for the above-mentioned dye-sensitized solar cell and a method for effectively utilizing solar light received by the above-mentioned dye-sensitized solar cell has been studied.
[Patent Document]
    [Document 1] Japanese Patent Application Publication No. 2005-019132